Method of and die mandrel for shaping curved tubes



Oct. 4, 1932. FORD T 1,881,121

METHOD OF AND DIE MANDREL FOR SHAPING CURVED TUBES Filed June 10, 1930 2 Sheets-Sheet l l N V E N R5 Pad 1 15m Veajs orz .Y' ungy ATTORN EYS Patented Oct. 4,

1 om'rnnfsflA'rss PATENT OFFICE 'raur. a. scan" AND unison YOUNG. or noursvrnnn, xnmucxr, nssrenons 5:0 mm:

' emnrnn WARE coaronnrron, or LOUISVILLE, xnnrucxr, a conronn'rron or 1mm- IIETEOD OF DIE MANDBEL FOB SHAPING CURVE TUBES Application filed June 10, 1980. Serial No. 480,125.

This invention relates to the art of sha ing tubes or the like, andmore particular y to an improved die mandrel, for instance, of the type disclosed in UnitedStates' Patent No. 1,353,714 to R. H. Biihling, September In the shaping of straight tubes into bends, the wall forming the inner curved portion thereof is compressed or upset as the bend is formed. This upsetting has atendency to increase its thickness, but is offset through the agency of a mandrel of the type referred to in said patent, by expanding the diameter of the tube during shaping operations. In

5 this manner the surplus material is distributed circumferentially effecting thereby a 'tube bend having walls of equal thickness throughout. However, straight tubes as commercially manufactured are seldom perfectly uniform in wall thickness so that they are subjected to difierentialstrains which efi'ect a torsional influence thereon as they are being forced over the die mandrel. Torsional tendencies might also b'eproduced during the shaping operation as a result of unequal heating of the tube or other irregular factor which will render one part of said tube more susceptible than another tostretching or compression under stresses. These varying in fluences often have the effect of twisting said tube from the plane in which it is initial- 1y started in shaping relationship with the die. Thus the resultant tubes often have to be subjected to a further operation to bring the axis into a single plane. j

The present invention provides means for confining every element of the tube during shaping operation so that regardlessof any irregular influences on said tube, its resultant bent formwill have its axis disposed in one plane.

The present invention also provides a method of shaping tubes over a die mandrel, which includes the step of forcing said mandrel and said tubes into keyed relationship during shaping operations.

In aconcrete'exemplification of the present invention, the tube in being forced over depression or groove provided in the tubeexpanding portion of the mandrel and extending lengthwise thereof. -In this manner a corresponding projection in the inside of the tube is formed during the bending operation, this projection on aging said depression and serving to key sai tube against twisting movement. This projection may take the form of a rib or key extending inside along the inner curved portion of the tube and may be forged by a correspondingly shaped groove or key-way in the inner curved ortion of the die mandrel. If desired, and if the torsional stresses are excessive, the inside surface of the outer curved portion of the tube bein bent ma be similarly (provided with a formed y a corres on ingly disposed ke way on the die man rel. Either one o'r'both of these ribs may be-provided. However, the inner curved portion of the tube is the portion which is subjected to greater metal displacing force,'so that a deeper rib or roection is formed thereon than would be formed in the inside of the outer tion of the tube. Therefore if only one rib is to be used, it is preferable to emplo the one tion of the tube.

curved por- The rib formed as a result of this improved bending may sometimes be objectionable. The present invention, therefore'further rovides means for removing this rib after 1t is formed, and after it has served its function but before the shaping operation is completed. This can be effected by providing in the path of the tube rib a projecting ed? which serves to iron out" or shear off said ri Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the appended claims, the invention itself, as to its objects and advantages, the mode ofits operation, and the manner of its organization, may be better understood by referring to the following description taken in connection withthe accompanying drawings forming a part thereof, in whic Figure 1 is a top plan view of the die mandrel,

Fig. 2 is a side elevation of the die mandrel,

25 whicli rnaybe frustoseonical tofacilitate the which extends lengthwisefand preferably of the tube after being forced along the die mandrel,

Fig. at is a bottom plan view of the tube after being forced along the (lie mandrel, 5 Fig. 5 is a topsplan viexv of a med fied form along the entire length of the curved part of said mandrel. As the tube is being forced along said mandrel it is expanded and the inside Wall is subjected to stresses due to the eccentric projection Ofi"the -'dief mandrel and of diejlmandrel, Fig. 6 is a top plan View of a fOIIl1 1. 0f mandrel designed to remove the' rib, FFigJ Tis a; seetion't'a'keii on thc line ofZFigQB J Fig. 8 is a side elevation partly in section of a tube afterbeing forcedover themandrel of Fig.6a1id*-" Y l Fig. 9 is a bottom plan view of a tube shown in Fig. 8. F-Lik -Ieference characters denote-like :parts t a everalfigures, of, the @drawings,

as following, descript n-amt i t 111- parts; vvillbe" identified by specific na es or convenience,butt-heyare intended I o e as genericintheir-application to-simi r parts astheartqvill permit.

In-the specific form shown in? netalwhich would otherwise tend to produce increased thickness... The key-way 1% acts, as a diefoi'Tthe upset portion of the tube and forms a rib'or key '15 along the inside surface of said tube. This rib 15 is positioned in keyed. relationship with the groove 14 thereby obviating the displacement of the elements the tube from their plane of movement.

mandrel maybe provided'with a'keyvay 16' which similarly forms a rib 17 on'theoutside curvature of-the tube. It should be noted that'the'outside' curved portion of the-tube and subjected to less stresses than the-inner Figs..- 1 and deformingof the metal takes place on the outside radius OfF-the tube than. on; the inside radiusefiThis. may result in deficient gripping relationship between said rib 17"a'nd' the engaging 'key Way' 16. Y To :compensate 'for die mandrelj has a shank -10,'one';end;of

entry of the tribe into. iorci ng relationship therewith, ,,i"I;he oth'er end of the shank 10 merges intothe bench-forming portion 11 having-an ou sidecurvature 12 which corresponds tothe-{curvature of the; resultant benttube and: whichihas a point A as a center: of its curve v The y axis 134' 'ofjlthe 4 mandrel is constituted; by a pluralityof inter-connected cur-vedelements, and includes a 'eircul-arportiori from. Bto vC .havi ng-A as a center,. a ci-r.-: cularportion from C to D having a point e3 .Q tQ BaI J ir u1a P rti to F ha inga point-.( raas a center, and theaxis .ofithe shank. 10 as a tangent; ,The inside curvature of thermandrelis-constituted --by; a circular portionflfro m J to K having A as acenter, and a circular portion from L to M'having Has a center, thesetwo circular portions being joined-thy atangential element K. to M. This rel'ationshipbetvveen the centers of the curvedelementsconstituting the mandrel has not been shown as a limitation tothe particu= lartype of. mandrel towhich the present invention can be applied but is merely indicat-.-- ed to give a. general idea of theshape of one parti culartype of mandrel to .which -r-the-in vention may be appliedl It is-notjntended to limit the adaptation of the present; invenl-: tion to any -'-particular-typeofdie, mandrelexcept to a mandrel over which the tube-is forced .endwise to curve lllie mandrel isl otgradually increasing diameter if the tube i's to-be expanded and is curved laterally-on given aneccentric lproj ection ifthe tube. is to becurved. 3, j To provide a suitable.v resistance' -against torsional tendenqy of the character ;abo'.{ve referred to, the inside curvature of the man drel is provided with ,agroo-ve or key-wayl,

0 thekey-Way M so that a wider rib is correspon'dingly formed, as shown in Fig. 5.

1 The ribs formed on the inside of the-tubes as a'result of forcing operations may in some cases. be objectionable. -To.eliminate these a-mandrel is provided of the type shown in Figs. 6 and 7., Inthis form the key-Way 18 extends; only partially along the inner or shorter wall of the mandrel .so as to forma Thisprojecting edge serves to iron out or desired theedge 20 may be sharpened and tempered accordingly. Ifan ironing action,

round ofi' this edge or provide a gradual apthe base curvature ofzthekey-way 18. F

I It should be noted that this projecting edge I shavings which collect vinthekey-Way 18 and may prevent them .from passing tothe end may eventually clog up. the key-WaylS. and

desirable. collection of scale and the like a conduit or holei2l isprovided between the projecting edge 20and the end of the mandrel to permitthescale to end of the mandrel. J I M A tubea made .bythe die mandrel shown in Figs. 6 and .7 is shown in Figs. 8'and9.

It should benoted that the rel ativerforcing these te'nd'to dis'tributeicircuinfefiiitially the "If desired, the oiitside curved portion of the dl-iringforcing operations is under tension ribs before the end-of t'l're shapingoperation,

projecting edge '20 in thepa h of the rib.

sheanofltherib. If ashearing action is however, is. desired, it, is preferred to slightly 1 preach-thereto by an extension merging. with 20 dams the passage of the scale and any collect in sufiicient amounts to affect the ultimate shape of the tube. To obviate this une passgout through the ot the tube-and die mandrel can be effected I portion." 'lhere'su'ltg'ds that a much lesser this possible deficiency in gripping relation v .-.ei1ip,thekey.- way 16 may be m-a'de Wider than v of the mandreh Such scale and shavings by drawing or forcing the mandrel through the tube or by forcing the tube over the die mandrel.

Of course, it is preferable to have the groove in the mandrel to form a rib in the tube because such rib does not weaken the wall, but where such weakness is not. important, the mandrel might have a rib to form a groove in the tube.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

1. A mandrel for expanding and curving tubes, said mandrel having an eccentric projection to expand and bend the tube, and a key-way extending along the inner curvature thereof, and adapted to forge a corresponding rib in the inside of the tube being forced over'the mandrel, whereby allof the elements of said tube are confined to plane movement during shaping operation.

2. A tube-expanding and curving mandrel having a body portion of gradually increasing diameter and laterally curved, a keyway thereon adapted to forge a corresponding rib inside the tube being forced over the mandrel, whereby the elements of said tube are confined to plane movement during shaping operations, and means for substantially eliminating said rib before said tube is advanced outside of engaging relationshi with said mandrel.

' 3. A tube-bending mandrel having a lat-.

erally curved body portion with a key-wag thereon adapted to forge a corresponding ri way thereon adapted to forge a corresponding rib on the inside of the tube being forced over the mandrel, and a projecting edge on said mandrel in the path of said rib, said edge being adapted to eliminate said rib before said tube is advanced away from forcing relationship with said mandrel.

7. The method of forming curved tubes, which includes forcing a straight tube over a die mandrel having a ke way on the inner surved surface, and there y forging the excess material of said tubes into the key-way during shaping operations, and substantially eliminating the rib formed thereby before said tube is advanced outside of engaging relationship with said mandrel.

8. A mandrel for expanding and curving tubes, said mandrel having a body portion of gradually increasing diameter and laterally curved, and a keyway extending lengthwise thereof and adapted to forge a correspondin rib in the plane of the center of curvature o the mandrel, and along the inner surface of the wall of the tube being forced over said mandrel, the interengagement of said rib and said key-way serving to confine the movement of the tube to said plane during the shaping operation.

9. The method of forming curved tubes, which includes forcing a straight tube over a curved mandrel of larger diameter than the internal diameter of the tube to thereby expand the tube, reduce the wall thickness and curve the tube, and forging a portion of the metal of the wall of the tube into an inwardly extending rib in the plane of curvature of the tube during the expanding and curving operation to thereby maintain the tube in a predetermined plane.

Signed at Louisville in the county of Jefferson and State of Kentucky this 29th day of May, 1930.

1 NELSON YOUNG.

PAUL H. FORD.

said mandrel for shearing off said rib before said tube is advanced away from forcing relationship with said mandrel, said mandrel having a conduit leading from the field of action of said cutting edge to the end of the mandrel for obviatin the cloggin of the key-way with metal s avings or sea es.

5. A tube-shaping mandrel having a keyway thereonadapted to forge a corresponding rib on the inner surface of the tube being forced over the mandrel, and a projecting edge on said mandrel in the path of said rib, said edge being adapted to" eliminate said rib before said tube is advanced away from forcing relationship with said mandrel, said mandrel having a conduit leadin from the field of action of said projecting e ge to the end of the mandrel for obviating the clogging of the key-way with scales.

6. A tube-shaping mandrel having a key- 

